The present invention relates to speech recognition apparatus and more particularly to such apparatus in which sequentially generated spectra are equalized and selected to improve accuracy of recognition upon comparison with data representing a vocabulary to be recognized.
Various speech recognition systems have been proposed heretofore including those which attempt to recognize phonemes and attempt to recognize and determine the pattern of behavior of formant frequencies within speech. While these prior art techniques have achieved various measures of success, substantial problems exist. For example, the vocabularies which can be recognized are limited; the recognition accuracy is highly sensitive to differences between the voice characteristics of different talkers; and the systems have been highly sensitive to distortion in the speech signal being analyzed. This latter problem has typically precluded the use of such automatic speech recognition systems on speech signals transmitted over ordinary telephone apparatus, even though such signals were easily capable of being recognized and understood by a human observer.
Among the objects of the present invention may be noted the provision of speech recognition apparatus providing improved accuracy of recognition; the provision of such apparatus which is relatively insensitive to frequency distortion of the speech signal to be recognized; the provision of such a system which is relatively insensitive to variations in speaking rate in the signal to be analyzed; the provision of such a system which will respond to different voices; and the provision of such apparatus which is of highly reliable and relatively simple and inexpensive instruction. Other objects and features will be in part apparent and in part pointed out hereinafter.